HW 4 - CS 359 HW 4 Problem 3 1 Registering the reference...

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CS 359 – HW 4 Hasan Al-Marzouqi Problem 3: 1. Registering the reference image to the target image: Different point sets were used for Points and new_Points. To be able to match the “Points” to “new_Points” all the points were picked based on structures that can be identified in both images such as sharp corners and places of intersections between lines. The function “cpselect” in Matlab was used to pick the points. Sum of Absolute Difference (SAD) was used as a similarity measure to estimate the accuracy of the registration. Initial value of SAD was calculated between the reference and the target image. The registration algorithm is supposed to minimize SAD. A perfect registration should result in a disparity value of zero. Using thin plate splines 13 control points were used and were successful in getting a disparity of 12.8 which is lower than the original value of 19.8 between the reference and target images. Using polynomial transformations 32 control points were needed. Results were similar for the three different orders and were all close to 16.5. This similarity might be caused by the nature of the problem and the high similarity between the original and the target image. The distribution of “points” and “new_Points” must have also affected this result. Trying to shift one of the points in “new_Points” for example away from its correct location will have very little effect in order 1 transforms but will have much more obvious effect using order 3. After reaching a certain number of points adding more points affects the higher order transformations more than its effect on the lower orders (they act as if they reached a stable state) which agrees with what is expected from the algorithm. Files registerAB.m, TPSpoints.mat and polypoints.mat were submitted using OAK. Running the command registerAB(input_points’,base_points’) after loading the corresponding set of points will the generates the results presented in this report. 2. Compromises between accuracy of registration at the homologous points and the overall behavior of the transformation: To test this part only one image was used “reference.tif”. A set of points was picked that are distributed evenly around the image and were used as the variable “Points”. “new_Points” was set to equal points except for a shift for one of the points. Original image reference.tif
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CS 359 – HW 4 Hasan Al-Marzouqi Each Point in “Points” correspond with the same point in new_Points except for point x that is matched with points x’. Using those two set the accuracy of the registration at the shifted points was measured by measuring the length of the TRE vector at the shifted point. TRE=
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This note was uploaded on 01/10/2010 for the course EE 291 taught by Professor Fitzpatrick during the Fall '05 term at Vanderbilt.

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HW 4 - CS 359 HW 4 Problem 3 1 Registering the reference...

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